The subject matter disclosed herein relates to rotating stall, incipient surge, and surge detection in a compression system, e.g., in an industrial centrifugal or axial compressor, or a gas turbine engine.
As compressors operate, performance of the compressor and associated process and equipment may be adversely affected by disruptive events in the compressor and interaction between performance characteristics of the compressor and other elements of the system. Examples of these disruptive events include surge, incipient surge and rotating stall events in the compression system. Surge can be described as large and self-sustaining pressure and flow oscillations in the compression system, resulting from the interaction between the characteristics of the compressor and those of surrounding equipment. This includes associated piping, vessels, valves, coolers, and any other equipment affecting the pressure, temperature, gas composition, and flow in the compressor. Other compressor parameters, such as rotating speed, consumed power or motor current will also be affected, because pressure and flow oscillations result in significant changes in the power consumed by the compressor. Stall, e.g., rotating stall, and incipient surge occur as the flow through the compressor is reduced to a point where flow distortions appear around the rotating and non-rotating components of the compressor, due to boundary layer separation, blocking part or all of the flow between, for example, two adjacent compressor blades. Stall can further lead to blockage of significant parts of compressor gas passages, thus severely altering performance characteristics of the compressor. Severe stall may result in significant pressure-flow pulsations that may be referred to as incipient surge. Rotating stall and incipient surge may lead to full compressor surge, with flow reversal through the compressor, however full surge may occur without noticeable advent of rotating stall, or incipient surge, or the two may occur simultaneously.
Thus, surge and stall events can be extremely disruptive to any process or equipment having a compression system, such as a refining or a chemical process, or turbine engine driving a generator in a power plant. Accordingly, accurate detection of these events and protection from these events based on the detection may operate to extend the life and increase intervals between outages of the compression equipment and associated process.